764 research outputs found
The Weibull-Geometric distribution
In this paper we introduce, for the first time, the Weibull-Geometric
distribution which generalizes the exponential-geometric distribution proposed
by Adamidis and Loukas (1998). The hazard function of the last distribution is
monotone decreasing but the hazard function of the new distribution can take
more general forms. Unlike the Weibull distribution, the proposed distribution
is useful for modeling unimodal failure rates. We derive the cumulative
distribution and hazard functions, the density of the order statistics and
calculate expressions for its moments and for the moments of the order
statistics. We give expressions for the R\'enyi and Shannon entropies. The
maximum likelihood estimation procedure is discussed and an algorithm EM
(Dempster et al., 1977; McLachlan and Krishnan, 1997) is provided for
estimating the parameters. We obtain the information matrix and discuss
inference. Applications to real data sets are given to show the flexibility and
potentiality of the proposed distribution
A genome-wide association study identified loci for yield component traits in sugarcane (Saccharum spp.).
Sugarcane (Saccharum spp.) has a complex genome with variable ploidy and frequent aneuploidy, which hampers the understanding of phenotype and genotype relations. Despite this complexity, genome-wide association studies (GWAS) may be used to identify favorable alleles for target traits in core collections and then assist breeders in better managing crosses and selecting superior genotypes in breeding populations. Therefore, in the present study, we used a diversity panel of sugarcane, called the Brazilian Panel of Sugarcane Genotypes (BPSG), with the following objectives: (i) estimate, through a mixed model, the adjusted means and genetic parameters of the five yield traits evaluated over two harvest years; (ii) detect population structure, linkage disequilibrium (LD) and genetic diversity using simple sequence repeat (SSR) markers; (iii) perform GWAS analysis to identify marker-trait associations (MTAs); and iv) annotate the sequences giving rise to SSR markers that had fragments associated with target traits to search for putative candidate genes. The phenotypic data analysis showed that the broad-sense heritability values were above 0.48 and 0.49 for the first and second harvests, respectively. The set of 100 SSR markers produced 1,483 fragments, of which 99.5% were polymorphic. These SSR fragments were useful to estimate the most likely number of subpopulations, found to be four, and the LD in BPSG, which was stronger in the first 15 cM and present to a large extension (65 cM). Genetic diversity analysis showed that, in general, the clustering of accessions within the subpopulations was in accordance with the pedigree information. GWAS performed through a multilocus mixed model revealed 23 MTAs, six, three, seven, four and three for soluble solid content, stalk height, stalk number, stalk weight and cane yield traits, respectively. These MTAs may be validated in other populations to support sugarcane breeding programs with introgression of favorable alleles and marker-assisted selectio
Fenologia de novas variedades copas de citros nos Tabuleiros Costeiros do Sul de Sergipe.
O Estado de Sergipe é considerado o quarto maior produtor de citros do Brasil (IBGE, 2014). Estima-se, que a área cultivada com citros esteja próximo aos 57 mil hectares, sendo que 98% desta área destina-se à produção de laranjas, as demais com o cultivo de limoeiros (limeiras ácidas) e tangerineiras. Os pomares estão localizados no Sul do estado, na região dos Tabuleiros Costeiros, compreendendo os municípios de Arauá, Boquim, Cristinápolis, Estância, Indiaroba, Itaporanga d ?ajuda, Itabaianinha, Lagarto, Pedrinhas, Riachão do Dantas, Salgado, Tomar do Geru, Umbaúba e Santa Luzia do Itanhy....bitstream/item/118382/1/Fenologia-de-novas-variedades-Cot136.pd
Levantamento expedito dos solos das reservas florestais de Linhares e Sooretama no Estado do Espírito Santo.
O presente trabalho teve como objetivo fornecer subsídios para melhor utilização das Reservas Florestais de Linhares e de Sooretama. Como o manejo florestal não exige mapas de levantamento de solos detalhado, elaborou-se nestas áreas, levantamento expedito dos solos. Este boletim técnico foi realizado para atender os professores e pesquisadores da Universidade Federal do Rio de Janeiro (UFRJ) - Projeto Biodiversidade, além de técnicos de outras entidades. A metodologia usada foi a desenvolvida pela Embrapa Solos. Foram usados como material básico, cartas do IBGE na escala 1:100.000. O mapa final é constituído por 12 unidades de mapeamento, com as seguintes classes de solos: LATOSSOLO VERMELHO, ARGISSOLO AMARELO, ESPODOSSOLOS e NEOSSOLOSbitstream/item/89239/1/bpd49-2004-sooretama.pd
Secular Evolution and the Formation of Pseudobulges in Disk Galaxies
We review internal processes of secular evolution in galaxy disks,
concentrating on the buildup of dense central features that look like
classical, merger-built bulges but that were made slowly out of disk gas. We
call these pseudobulges. As an existence proof, we review how bars rearrange
disk gas into outer rings, inner rings, and gas dumped into the center. In
simulations, this gas reaches high densities that plausibly feed star
formation. In the observations, many SB and oval galaxies show central
concentrations of gas and star formation. Star formation rates imply plausible
pseudobulge growth times of a few billion years. If secular processes built
dense central components that masquerade as bulges, can we distinguish them
from merger-built bulges? Observations show that pseudobulges retain a memory
of their disky origin. They have one or more characteristics of disks: (1)
flatter shapes than those of classical bulges, (2) large ratios of ordered to
random velocities indicative of disk dynamics, (3) small velocity dispersions,
(4) spiral structure or nuclear bars in the bulge part of the light profile,
(5) nearly exponential brightness profiles, and (6) starbursts. These
structures occur preferentially in barred and oval galaxies in which secular
evolution should be rapid. So the cleanest examples of pseudobulges are
recognizable. Thus a large variety of observational and theoretical results
contribute to a new picture of galaxy evolution that complements hierarchical
clustering and merging.Comment: 92 pages, 21 figures in 30 Postscript files; to appear in Annual
Review of Astronomy and Astrophysics, Vol. 42, 2004, in press; for a version
with full resolution figures, see
http://chandra.as.utexas.edu/~kormendy/ar3ss.htm
Dynamics of Barred Galaxies
Some 30% of disc galaxies have a pronounced central bar feature in the disc
plane and many more have weaker features of a similar kind. Kinematic data
indicate that the bar constitutes a major non-axisymmetric component of the
mass distribution and that the bar pattern tumbles rapidly about the axis
normal to the disc plane. The observed motions are consistent with material
within the bar streaming along highly elongated orbits aligned with the
rotating major axis. A barred galaxy may also contain a spheroidal bulge at its
centre, spirals in the outer disc and, less commonly, other features such as a
ring or lens. Mild asymmetries in both the light and kinematics are quite
common. We review the main problems presented by these complicated dynamical
systems and summarize the effort so far made towards their solution,
emphasizing results which appear secure. (Truncated)Comment: This old review appeared in 1993. Plain tex with macro file. 82 pages
18 figures. A pdf version with figures at full resolution (3.24MB) is
available at http://www.physics.rutgers.edu/~sellwood/bar_review.pd
An HPLC method to determine phenolic compounds of plant extracts: application to Byrsonima crassifolia and Senna alata leaves.
Background: The Amazonian Region has a variety of medicinal plants with bioactive compounds, whose characterization could present the potential for sustainable development. Objectives: A method for separating, identifying, and quantifying a mixture of nine phenolic compounds (gallic acid, 3-hydroxybenzoic acid, p-coumaric acid, catechin, myricetin, rutin, quercetin, kaempferol, and cyanidin) was developed, validated, and applied to analyze aqueous and hydroethanolic extracts from Byrsonima crassifolia (L.) Kunth and Senna alata (L.) leaves. Materials and Methods: The separation was carried out by HPLC, using a Shim-pack VP-ODS C18 column (5 μm, 150 x 4.6 mm) at 40°C. Detection was performed at 254 nm and separation occurred in 35 min. Results: The optimized method was validated for each of the nine phenolic compounds. The calibration curve for the phenolic compound standards showed suitable linear fitting and exhibited correlation coefficients greater than 0.990. The LOD and LOQ varied between 6.2807 - 14.8851 μg mL-1 and 6.8002 - 16.0071 μg mL-1, respectively. The method was found to be robust for changes of ±2 ml in mobile phase composition. Byrsonima crassifolia aqueous extracts indicated contents of gallic acid, catechin, rutin, and cyanidin whereas hydroethanolic one did not show the first substance. Senna alata aqueous extract presented only 3-hydroxybenzoic acid and rutin whereas myricetin, cyanidin, quercetin, and kaempferol were also identified in the hydroethanolic one. Conclusion: The HPLC method is efficient, precise, accurate, and sensitive to determining phenolic compounds in plant extracts and it is recommended for efficient assays in routine work
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